The present invention comprises a composition and a method for reduction of the content of organically bound sulphur in a hydrocarbon composition in a cracking process. The invention also comprises a method for using a composition for reducing the sulphur content in a hydrocarbon composition.
Legislation regarding environmental aspects sets a limit for the sulphur content in petrol. Petrol is a direct contributor to SOx-effluents, and is also poisoning car catalysts at low temperatures (low temperature activity). The main sulphur contributor in petrol is FCC-naphtha (fluid catalytic cracking-naphtha), and efforts to obtain an effective reduction of the sulphur content must therefore be based on said petrol component.
It is also known to reduce the sulphur content in FCC-naphtha by hydrogenation of a flow of FCC-feed or of FCC-naphtha. Both methods require high investment costs and are expensive to operate. A third method for reducing the sulphur content in FCC-naphtha is to lower the end boiling point of FCC-naphtha since the main part of the sulphur component in FCC-naphtha exist in the heavy fraction. A disadvantage concerning the latter method is that some of the components in FCC-naphtha having highest octane number are also present in the heavy fraction. A lowering of the end boiling point will also reduce the octane number in addition to reducing the yield of naphtha.
WO-86/06090 describes a method for oxidation of SO2 into SO3 wherein a hydrocarbon composition is contacted with a material existing of a spinel composition including an alkaline earth metal, an aluminium component and one or several metals, including zinc. Reducing the sulphur content in FCC-naphtha is not mentioned in WO-86/06090.
From WO-87/06157 is it further known a composition comprising a spinel, preferably a magnesium-aluminium-containing spinel, which has been impregnated with one or several metals to promote oxidation of SO2 to SO3. The metals are preferably selected from the group consisting of IB, IIB and/or the group of platinum metals.
WO 98/48480 describes a process for sulphur oxide sorption using hydrotalcite materials as contact solids. Large crystalline sheet materials having increased sorption of SOX are provided by incorporation of certain organic acid anionic species to modify the hydrotalcite/brucite structure. WO97/48480 does not describes elimination of sulphur as such but elimination of SO2. Eliminating sulphur and eliminating S2 from hydrocarbons are two completely different chemical processes.
Prior art mentioned above comprises compositions for oxidation of SO2 into SO3 in the regenerator of a catalytic cracker. Regarding this process, it is not desirable with SOx-effluents from environmental aspects, and effluents of sulphur made of H2S is more convenient for most refineries, wherein H2S is converted into elementary sulphur. A composition for reducing SOx-effluents, in most cases a metal oxide (MO), possesses the following effect:
oxidizing SO2 into SO3 in the 2 SO2+O2=2SO3 regenerator
reacting with SO3 and create a metal SO3+MO=MSO4 sulphate
submit sulphur as H2S in the cracker, MSO4+4H2=MO+H2S+3H2O and create the oxide state of the metal
The prior art mentioned above does not refer to reduction of the sulphur content in a hydrocarbon composition or FCC-naphtha as in the present invention. Reduction of the sulphur content in a hydrocarbon composition or in a hydrocarbon composition which is cracked, is obtained according to the composition of the present invention, and described according to the following reaction:
RS+H2=R+H2S
According to the above mentioned, the chemistry concerning the reduction of the SOx-effluent and the reduction of the sulphur content in FCC-naphtha is different. A composition, which reduces SOx-effluent, can not be expected to reduce the sulphur content in a hydrocarbon composition or in a hydrocarbon composition which is cracked catalytic.
A composition and method for reducing the sulphur content in FCC-naphtha, which uses a special catalyst or composition, added a known FCC-catalyst comprising a zeolite and a matrix, is known. A catalyst or composition as such which reduces the sulphur content in FCC-naphtha, is described by Wormsbecher et al. in EP-A1-609971, wherein a composition comprises a Lewis acid deposited on an aluminium oxide carrier. EP-A1-609971 also describes that the Lewis acid may comprise components and compounds including Zn, Cu, Ni, Ag, Cd, Lu, Su, Hg, Tl, Pb, Bi, B, Al and Ga deposited at aluminium oxide. The above mentioned patent application also refer to compositions which comprises aluminium oxide and spinel which may be added to catalytic cracking catalysts to reduce the SOx-effluent during oxidation and regeneration of the FCC-catalyst. So far, the industry has not developed compositions comprising catalytic splitting catalysts for reducing the sulphur content in products as petrol and diesel.
EP 798362, Ziebarth et. al describes TiO2-containing compositions which reduce the sulphur content of the product flow from a catalytic cracking-catalyst. The present invention comprises a composition for reducing the sulphur content of a hydrocarbon composition and of a catalytic cracked hydrocarbon composition wherein the composition comprises a carrier made of a hydrotalcite material, different from i.a. Wormsbecher et al and Ziebarth et al.
The present invention provides a composition for reducing the sulphur content in a hydrocarbon composition wherein said composition comprises a hydrotalcite material which is impregnated with a Lewis acid, and optionally an FCC-catalyst. The hydrotalcite material impregnated with the Lewis acid is added as a separate component, or incorporated in the matrix of the FCC-catalyst. Said Lewis acid is selected from the group comprising elements and compounds of the transition metals, preferably Zn, Cu, Ni, Co, Fe and Mn, most preferably Zn. The Lewis acid is also selected from the group comprising elements and compounds of the lanthanides or the actinides. Preferably, the composition of the present invention is promoted with a hydrogen transfer promoter, preferably made of Pt.
Further, the present invention provides a method for reduction of the content of organically bound sulphur in a hydrocarbon composition in a cracking process, wherein said composition is contacted with a composition promoted with a hydrogen transfer promotor, comprising a hydrotalcite material impregnated with a Lewis acid and a FCC-catalyst. Said Lewis acid is selected from the group comprising elements and compounds of the transition metals, preferably Zn, Cu, Ni, Co, Fe and Mn, most preferably Zn. The Lewis acid is also selected from the group comprising elements and compounds of the lanthanides and the actinides. Said hydrotalcite material is preferably promoted with a hydrogen transfer promoter, preferably made of Pt. According to the method for reducing the sulphur content in a hydrocarbon composition in a cracking process, said hydrotalcite material impregnated with the Lewis acid is added as a separate component, or has been incorporated in the matrix of the FCC-catalyst. The hydrocarbon composition comprises FCC-naphtha, LCO and/or HCO-fractions. Further, the use of a composition comprising a hydrotalcite material, which has been impregnated with a Lewis acid, and optionally mixed with an FCC-catalyst for reducing the sulphur content in a hydrocarbon composition, is also disclosed. The Lewis acid is selected from group comprising elements and compounds of the transition metals, and preferably Zn, Cu, Ni, Co, Fe and Mn, most preferably Zn. Further, said Lewis acid is selected from the group comprising elements and compounds of the lanthanides and the actinides. It is preferred using a composition promoted with a hydrogen transfer promoter, preferably made of Pt. Use according to the present invention is preferably a hydrocarbon composition which is a cracked hydrocarbon composition made of FCC-naphtha. Further on, use of a hydrotalcite material impregnated with a Lewis acid is encompassed, in which said hydrotalcite material has been added as a separate component, or has been incorporated in the matrix of the FCC-catalyst.